A content addressed storage device configured to maintain content address mapping is disclosed. A data object to be stored on the content addressed storage device and a local data object identifier by which the data object is known to the sending source are received from a sending source. A content address to be associated with the data object on the content addressed storage device is determined based at least in part on the contents of the data object. The data object is stored on the content addressed storage device in a storage location associated with the content address. A mapping that associates the local data object identifier with the content address is maintained on the content addressed storage device.